Radio Frequency Identification (RFID) is an emerging area of technology with numerous applications, particularly in the field of inventory control. RFID is an automatic identification method, relying on storing and remotely retrieving data using devices that are called RFID tags or transponders. An RFID tag is a small object that can be attached to, or incorporated into, a product, animal, person or other stored object and contains silicon chips and antennas to enable it to receive and respond to radio-frequency queries from an RFID transceiver. When an RFID tag is combined with one or more sensors, the RFID tag can report the information that is measured by the sensors. A passive RFID tag requires no internal power source, while active RFID tags do require a power source. A passive RFID tag is better for inventory control for long-term storage items because the use of battery power to operate the RFID tag is ordinarily unacceptable. For such applications, a passive RFID tag combined with a sensor that also does not need power for its operation is critical.
RFID tags have found numerous useful applications in the storage of a diverse number of commodities, but they still suffer from the drawbacks, limitations and shortcomings of being temperature-insensitive because they do not identify excessively high or low temperatures. During storage, if the proper temperature range is not maintained, the useful lifetime, capability, safety, and many other characteristics of the stored object can be deleteriously degraded or lost, which can lead to a number of undesirable, and possibly dangerous, results. Currently available RFID tags do not promptly identify undesirable conditions where an excessively high or low storage temperature can harm the stored object.
Thermal fuses have been used to monitor excessively high temperatures with a certain amount of success. A thermal fuse is defined as a cutoff device which uses a one-time fusible link. While a thermostat automatically resets itself whenever the temperature drops, the thermal fuse is more like an electrical fuse: a single-use device that cannot be reset and must be replaced when it fails or is triggered. Conventional thermal fuses cut off only at a high temperature, and not at temperatures that are lower than room temperature. Thus, there has been a long-felt need for a thermal fuse that operates at lower temperatures, as well as high temperatures that inform the user that the required storage temperatures have been exceeded that does not suffer from the disadvantages, shortcomings and limitations of prior art temperature-insensitive RFID tags and high temperature only thermal cutoff fuses. Up until now, the long-felt need for an all temperature-sensitive RFID tag has not been met.